Safety of COVID-19 Vaccination in 

Pregnancy, Interim Data from the 

Vaccine Safety Datalink 

Elyse O. Kharbanda, MD, MPH 

HealthPartners Institute 

Advisory Committee on Immunization 

Practices 

September 22, 2021 

1 
 

Overview 

• Data from the Vaccine Safety Datalink (VSD) 

• Receipt of COVID-19 vaccines before and during 

pregnancy 

• Spontaneous abortion following COVID-19 

vaccination 

• Stillbirth surveillance 

2 
Vaccine Safety Datalink 

3 
 

 

 

 

 

 

 

Identifying ongoing pregnancies in the 

Vaccine Safety Datalink (VSD) 

• VSD previously developed and validated pregnancy 

episode algorithm (PEA) applied to identify completed 

pregnancies 

• PEA used in prior VSD studies of maternal Tdap and IIV safety 

• Dynamic pregnancy algorithm (DPA) developed and 

validated to identify and date ongoing pregnancies1 

• DPA incorporates diagnoses and procedure codes from health 

care visits, clinical variables (e.g., EDD, LMP), updated weekly 

• DPA made our work on safety of COVID-19 vaccine in 

pregnancy possible 

1Naleway et al. Vaccine Safety Datalink infrastructure enhancements for evaluating the safety of maternal 

vaccination. Therapeutic Advances in Drug Safety. 2021 

4 
 

 

 

COVID-19 vaccine doses administered and pregnancy in VSD,

Dec 14, 2020 – Jul 31, 2021, of 122,998 pregnancies: # of Pregnant Women 

• 10,178 pregnancies with ≥1 vaccine dose prior to pregnancy

• 6,792 pregnancies with 2 vaccine doses prior to pregnancy 

8000 

7000 

0 

1000 

2000 

3000 

4000 

5000 

6000 

Prior to pregnancy

1st Trimester

2nd Trimester

Janssen/No 2nd Dose

Dose not administered

1st Trimester

2nd Trimester

3rd Trimester

Janssen/No 2nd Dose

Dose not administered

2nd Trimester

3rd Trimester

After pregnancy

Janssen/No 2nd Dose

Dose not administered

3rd Trimester

After pregnancy

Janssen/No 2nd Dose

Dose not administered 

Prior to pregnancy 1st Trimester 2nd Trimester 3rd Trimester 

Dose 2 

Timing 

Dose 1 

Timing 

5 
8000 

7000 

6000 

5000 

4000 

3000 

2000 

1000 

0 

Dose 2 

Timing 

# of Pregnant Women 

Prior to pregnancy

1st Trimester

2nd Trimester

Janssen/No 2nd Dose

Dose not administered

Prior to pregnancy 

1st Trimester

2nd Trimester

3rd Trimester

Janssen/No 2nd Dose

Dose not administered

1st Trimester 

2nd Trimester

3rd Trimester

2nd Trimester After pregnancy Janssen/No 2nd Dose

Dose not administered

3rd Trimester 

3rd Trimester

After pregnancy

Janssen/No 2nd Dose

Dose not administered 

Dose 1 

Timing 

6 

 

COVID-19 vaccine doses administered and pregnancy in VSD,

Dec 14, 2020 – Jul 31, 2021, of 122,998 pregnancies: 

• 31,080 pregnancies with ≥1 vaccine during pregnancy 

• 23,310 pregnancies with 2 vaccine doses during pregnancy 
 

Kharbanda et al. Spontaneous 

Abortion Following COVID-19 

Vaccination During Pregnancy. 

JAMA. 2021 Sep 8. doi: 

10.1001/jama.2021.15494. 7 
 

 

 

 

 

COVID-19 vaccine in pregnancy and 

spontaneous abortion (SAB) surveillance 

• Identified SABs and ongoing pregnancies 6–19 weeks’ 

gestation 

• SABs assigned to a 4-week surveillance period 

• Ongoing pregnancies, including pregnancy time prior to SAB, 

assigned to ≥1 surveillance periods

• Using GEE, odds of exposure to COVID-19 vaccine in 28 

days prior to SAB compared to odds of exposure to 

COVID-19 vaccine among ongoing pregnancies in 28 days 

prior to index date 

• Adjusting for gestational age, maternal age, receipt of prenatal 

care, race/ethnicity, and VSD site 

8 
 

Example of how SABs and ongoing pregnancies 

classified across seven surveillance periods 

Kharbanda et al. Spontaneous Abortion Following COVID-19 Vaccination 

During Pregnancy. JAMA. 2021 Sep 8. doi: 10.1001/jama.2021.15494. 9 
 

 

COVID-19 vaccines received during pregnancy

(Dec 15, 2020 – Jun 28, 2021, for 105,446 unique 

pregnancies <20 weeks’ gestation) 

Seven surveillance periods

(Dec 15, 2020 – Jun 28, 2021) 

Ongoing

Pregnancies 

N (%) 

Spontaneous

abortions 

N (%) 

All included pregnancies 92,286 13,160 

Vaccine type 

Janssen / J&J 480 (0.5) 48 (0.4) 

Moderna 5638 (6.1) 675 (5.1) 

Pfizer 7463 (8.1) 804 (6.1) 

Kharbanda et al. Spontaneous Abortion Following COVID-19 Vaccination During 

Pregnancy. JAMA. 2021 Sep 8. doi: 10.1001/jama.2021.15494. 

10 
 

 

COVID-19 vaccines in prior 28 days 

(Dec 15, 2020 – Jun 28, 2021, 264,104 pregnancy-periods) 

Ongoing

pregnancy-periods 

Spontaneous

abortions 

N 

COVID-19 

vaccination 

N 

COVID-19 

vaccination 

n (%) n (%) 

All pregnancy-periods* 250,944 20,139 (8.0) 13,160 1128 (8.6) 

6–8 weeks gestation 57,355 5196 (9.1) 5238 482 (9.2) 

9–13 weeks gestation 88,982 6067 (6.8) 6652 528 (7.9) 

14–19 weeks gestation 104,607 8876 (8.5) 1270 118 (9.3) 

16–24 years 37,210 1325 (3.6) 1433 69 (4.8) 

25–34 years 156,166 12,451 (8.0) 6640 493 (7.4) 

35–49 years 57,568 6363 (11.1) 5087 566 (11.1) 

*Individual pregnancies may contribute data for more than one surveillance period, pregnancies <20 weeks’ gestation included 

Kharbanda et al. Spontaneous Abortion Following COVID-19 Vaccination During 11 

Pregnancy. JAMA. 2021 Sep 8. doi: 10.1001/jama.2021.15494. 
 

 

 

 

 

 

COVID-19 vaccines in prior 28 days 

(Dec 15, 2020 – Jun 28, 2021, 264,104 pregnancy-periods) 

Ongoing

pregnancy-periods 

Spontaneous

abortions 

N 

COVID-19 

vaccination 

N 

COVID-19 

vaccination 

n (%) n (%) 

Hispanic 86,108 5207 (6.0) 4346 322 (7.4) 

White, non-Hispanic 81,834 7571 (9.3) 4272 373 (8.7) 

Asian 35,938 4433 (12.3) 2028 262 (12.9) 

Unknown / other 28,274 2213 (7.8) 1435 123 (8.6) 

Black, non-Hispanic 18,790 715 (3.8) 1079 48 (4.4) 

<= 1 antenatal visits 89,913 6850 (7.6) 3203 244 (7.6) 

>= 2 antenatal visits 161,031 13,289 (8.3) 9957 884 (8.9) 

*Individual pregnancies may contribute data for more than one surveillance period, pregnancies 

<20 weeks’ gestation included 

Kharbanda et al. Spontaneous Abortion Following COVID-19 Vaccination During 12

Pregnancy. JAMA. 2021 Sep 8. doi: 10.1001/jama.2021.15494. 
 

 

 

 

COVID-19 vaccines in prior 28 days

Dec 15, 2020 – Jun 28, 2021, 264,104 pregnancy-periods 

Ongoing pregnancies Spontaneous abortions 

N 

COVID 

vaccination 

N 

COVID 

vaccination 

n (%) n (%) 

Dec 15, 2020–Jan 11, 2021 36,964 711 (1.9) 1767 21 (1.2) 

Jan 12, 2021–Feb 8, 2021 36,981 1696 (4.6) 2097 68 (3.2) 

Feb 9, 2021–Mar 8, 2021 37,030 2322 (6.3) 1871 97 (5.2) 

Mar 9, 2021–Apr 5, 2021 37,144 4934 (13.3) 1903 204 (10.7) 

Apr 6, 2021–May 3, 2021 36,191 5654 (15.6) 1864 330 (17.7) 

May 4, 2021–May 31, 2021 34,545 3485 (10.1) 1811 272 (15.0) 

Jun 1, 2021–Jun 28, 2021 32,089 1337 (4.2) 1847 136 (7.4) 

*Individual pregnancies may contribute data for more than one surveillance period, pregnancies <20

weeks’ gestation included 

Kharbanda et al. Spontaneous Abortion Following COVID-19 Vaccination During 13 

Pregnancy. JAMA. 2021 Sep 8. doi: 10.1001/jama.2021.15494. 
 

 

 

 

 

 

 

Adjusted Odds Ratios for receipt of COVID-19 vaccine 

in 28 days prior to SAB, Dec 15, 2020 – Jun 28, 2021 

aOR (95% CI) 

Full population 1.02 (0.96–1.08) 

By gestational age strata 

6–8 weeks 0.94 (0.86–1.03) 

9–13 weeks 1.07 (0.99–1.17) 

14–19 weeks 1.08 (0.89–1.29) 

By vaccine type 

mRNA-1273, Moderna 1.03 (0.94–1.11) 

BNT162b2, Pfizer-BioNTech 1.03 (0.95–1.11) 

aOR = adjusted odds ratio; SAB= spontaneous abortion 

GEE models adjusted for gestational age group, study month, site, maternal age group, number 

of antenatal visits, and race/ethnicity and accounted for repeated ongoing pregnancies 

Kharbanda et al. Spontaneous Abortion Following COVID-19 Vaccination During 14

Pregnancy. JAMA. 2021 Sep 8. doi: 10.1001/jama.2021.15494. 
 

 

 

Limitations, summary and next steps 

• Limitations 

• Spontaneous abortion cases not chart confirmed 

• Unable to adjust for some potential confounders 

• Among women with spontaneous abortions, 

adjusted odds of COVID-19 vaccine exposure were 

not increased in the prior 28 days, compared to

women with ongoing pregnancies 

• Future individually matched case-control study 

planned, with all spontaneous abortion cases chart 

confirmed 

15 
 

 

 

Monthly surveillance for stillbirths 

following COVID-19 vaccination 

• Potential stillbirth cases with COVID-19 vaccine 

exposures identified each month 

• To increase sensitivity, included SABs at 18–19 

weeks’ gestation 

• All potential cases chart reviewed by sites 

• All potential cases adjudicated by Yale OB team 

• For confirmed stillbirths, using adjudicated date 

and gestational age at fetal demise, evaluated 

timing of COVID-19 vaccine exposures 

16 
 

 

 

 

 

Monthly surveillance for stillbirths following COVID-19

vaccination (Dec 2020 – Jul 2021, 11,300 live births in VSD during 

this period received COVID-19 vaccine during pregnancy) 

Outcome date 

Stillbirths or 

late SABs* 

(N) 

Stillbirths or 

late SABs with 

COVID-19 vaccine* 

(N) 

Excluded** 

(N) 

Confirmed stillbirths 

with COVID-19 

vaccine exposure 

during pregnancy 

(N) 

December 2020 47 0 . 0 

January 2021 108 3 3 0 

February 2021 97 7 6 1 

March 2021 89 8 5 3 

April 2021 104 20 12 8 

May 2021 90 22 16 6 

June 2021 94 25 20 5 

July 2021 41 7 4 3 

Dec 2020 – Jul 2021 670 92 66 26*** 

Late SABs = spontaneous abortions estimated to occur at 18- or 19-weeks’ gestation 

*Based on automated pregnancy algorithm; **Exclusions due to: SAB (n=41) ongoing pregnancy (n=2), 

live birth (n=10), ectopic pregnancy (n=1) therapeutic abortion (n=9), and records not available (n=3); 17 ***Consistent with expected background rates 
18 

Gestational age at stillbirth in weeks 

Mean = 29.5 weeks (sd=6.6 weeks); Range = 20 - 40 weeks (n=26) 18 
19

 

Pregnancy or birth complications associated 

with stillbirth in cases with COVID-19 vaccine 

exposure (n=26) 

Complication n (%) 

One or more complications associated with stillbirth 25 (96) 

Umbilical cord or placental complication

(e.g., true knot, tight nuchal cord, placenta <10%) 19 (73) 

Obstetric complication 

(e.g., placental abruption, chorioamnionitis) 18 (69) 

Maternal comorbidity

(e.g., hypertension, diabetes) 16 (62) 

Fetal condition 

(e.g., congenital CMV) 7 (27) 

Multiple gestation pregnancy with complications 1 (4) 

19 
20

 

 

Timing between COVID-19 vaccination and stillbirth, 

by dose 

Dose 1 (n=26) 

Range = 8 - 140 days 

Dose 2 (n=16) 

Range = 3 - 112 days 

20 
21

 

 

 

Timing between vaccination and stillbirth, 

by manufacturer 

J&J (n=4) 

Range = 13 - 111 days 

Moderna (n=17) 

Range = 3 - 140 days 

Pfizer (n=21) 

Range = 6 - 129 days 

21 
 

 

 

 

 

Limitation, summary and next steps 

• Limitation 

• Stillbirth surveillance is descriptive, no comparison group 

• Monthly stillbirth surveillance with chart review and 

adjudication has identified 26 stillbirths following

COVID-19 vaccination from Dec 2020 – Jul 2021 

• Nearly all cases with known stillbirth risk factors 

• No concerning patterns identified related to timing of

vaccine exposure or stillbirth etiology 

• Future case-control study planned 

22 
 

Our Team 

HealthPartners 

• Elyse Kharbanda, Project Director 

• Malini DeSilva 

• Gabriela Vazquez-Benitez 

• Jon Alpern 

• Leslie Kuckler 

• Jingyi Zhu 

• Jacob Haapala 

• Sunita Thapa 

• Sheryl Kane 

• Nicole Trower 

Yale University 

• Heather Lipkind, Co-Project Director 

• Uma Reddy 

• Sangini Sheth 

• Christina Ackerman 

• Victoria Greenberg 

Kaiser Northwest 

• Kimberly Vesco 

• Allison Naleway 

• Brad Crane 

CDC 

• Christine Olson 

• Mike McNeil 

• Eric Weintraub 

Other VSD sites 

• Nicola Klein 

• Matt Daley 

• Darios Getahun 

• Stephanie Irving 

• Mike Jackson 

• Joshua Williams 

• Simon Hambidge 

• Jim Donahue 

23